摘要:

Living and fossil megaspores produced bySelaginella(Lycopsida) and its extinct ancestors form distinctive (and occasionally iridescent) exines. Ultrastructural studies of these spores have provided data that demonstrate a colloidal mode of development which in turn implies a degree of self‐assembly in the construction of these exines. We present here experimental evidence in support of the theory of selaginellalean megaspore exine construction by depletion flocculation. Iridescent colloidal flocculations of polystyrene latex particles demonstrate an ultrastructural organization virtually indistinguishable from that of the biological system, and clearly demonstrate that self‐assembly of complexSelaginellaexines by a relatively simple construction process is plausi

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb00752.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The diversity of the Iberian vascular flora has been investigated using WORLDMAP versions 3.08 and 3.18. Two data sets scoring plant distributions as presences within the Iberian Peninsula were compiled; one for 2133 species at 50 × 50 km grid and the other for 801 species at 10 × 10 km map grids. Patterns of biodiversity were determined using the diversity measures of species richness, range‐size rarity and character richness diversity. Using the diversity measures, combined with an area selection method, maps of priority areas were calculated using iterative procedures. Near minimum sets (NMSs) for both scales were calculated. Comparison of the NMS for the 10 × 10 km grid with the near minimum set for existing reserves (NMSER) showed that at least 2% more of the land surface would be required above and beyond the existing protected area network, currently comprising 6% of the area, to ensure representation of all species at least once as listed within the present data‐base. It is demonstrated that reserve systems selected on a variety of different criteria are suboptimal when compared to particular groups of target organisms with a definite goal of representation for conservation. Calculating efficiency of existing reserve systems and accounting for all taxa identifies precisely the extra required areas for the protected area system to satisfy particular goals of represen

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb00753.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The present study is based on a re‐investigation of the vegetative and reproductive structures of the West African family Scytopetalaceae. Special emphasis is paid to inflorescence morphology and seed anatomy. The inflorescences of all genera of Scytopetalaceae can be interpreted as derived from panicles through reductions and structural changes. Thyrsoids prevail, but panicles, botryoids and racemes occur as well. Within the family cauliflory appears as the derived condition. Seed coat structure is extremely simplified and very stable in the Scytopetalaceae. The horny endosperm contains amyloid as the main storage compound. The presence of two obviously different forms of ruminate endosperm indicates that rumination arose twice within the family. The neotropical genusAsteranthos(Lecythidaceae) agrees in almost all relevant characters with the Scytopetalaceae. Therefore the proposed inclusion ofAsteranthosin the latter family is fully confirmed. Scytopetalaceae, Lecythidaceae, Foetidiaceae and Napoleonaeaceae apparently form a natural alliance. Two new subfamilies (Scytopetaloideae, comprisingScytopetalum, Oubanguia, andAsteranthos;Rhaptopetaloideae comprisingRhaptopetalum, PierrinaandBrazzeia) are proposed and fully describe

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb00754.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Fifty‐eight quantitative and qualitative exomorphological characters were recorded on 48 herbarium specimens belonging to rhizomatous species belonging to the genusPoa.These were treated as OTUs and analysed, together with the data from caespitose species treated in a previous paper, using cluster analysis, principal component analyses and stepwise discriminant analyses. The following hypotheses are proposed and discussed. (1) There is no evidence supporting the hypothesis that growth habit characterizes supraspecific entities. (2)P. trivialis, P. secunda, P. subenervisand probablyP. compressaseem to be well defined species; those remaining are not discriminated through phenetic analysis. (3) There are no phenetic gaps between the rhizomatous species included in theP. oligeria—P. yaganica‐P. chrysanthacomplex and the caespitoseP. hachadoensisit is not clear that this single character supports its segregation. (4) The obscurity of the pattern of the species related toP. pratensis‐P. nemoralisis probably explained by the capability ofP. pratensisto introgress with taxonomically distant species and by the possibility of seasonal intraindividual variation of some characters. (5) The geographical origin of some species postulated as introduced seems to be d

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb00755.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The system of tree architecture proposed by Hallé and Oldeman consists of 23 models named after botanists playing leading roles in elucidating tree architecture. This system gives no indication why other models do not occur. A symbolism is presented here which can serve as a shorthand in recording tree architectures without assumptions about models. and immediately interpretable. Using this symbolism to represent the models proposed by Hallé and Oldeman permits creation of general rules of tree architecture. some of which raise interesting theoretical questions. Two further tree models that might well be expected to exist and several which would not be expected. are describe

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb00756.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A developmental variant, in which the contact zone between female cone scales is ectopically expressed in many female cones ofCupressus sempervirens, is common in trees growing in Israel. There are two phenotypes: type A with grooves emerging from the contact zone between two scales, and type B with a blind groove in the inner area of a scale. Some scales show a combination of both. These structures are formed constantly, but in different proportions in individual cones, trees and populations. Within the cone, more ectopic indentations are found in the basal scales. The female cones of other members of the Cupressaceae examined, namelyCupressus macrocarpa, C. arizonicaandThuja orientalis, did not have ectopic indentations.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb00757.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

In the past, the two species ofCourtoisinawere placed either inCyperusL.,MariscusVahl, or inCourtoisiaNees (nowCourtoisinaSojak). While these species show undoubted external similarities to bothCypmandMuriscus, they differ by their widely winged glumes and the arrangement of the veins of the glumes. They also differ profoundly fromMariscusand most species ofCypmin anatomical characteristics, and it is concluded that these differences warrant separate generic status.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb00758.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Book reviewed in this article:Natural Woodland. Ecolosy and Conservation in Northern Temperate Regom, by George F. Peterken.The Flora of Hampshire, by Anne Brewis, Paul Bowman and Francis Rose.Ainsworth and Bisby's Dictionary of the Fungi, by D.L. Hawksworth, P.M. Kirk, B.C. Sutton and D.N. Pegler.Aduances in Compositae Systematics, edited by D.J.N. Hind, C. Jeffrey and G.V. PopeSoil Fungi in Qatar and other Arab Countries, by A.H. Moubasher.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1996.tb00759.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY